Abstract
DAPK-1 (death-activated protein kinase) has wide ranging functions in cell growth control; however, DAPK-1 interacting proteins that mediate these effects are not well defined. Protein-protein interactions are driven in part by linear interaction motifs, and combinatorial peptide libraries were used to identify peptide interfaces for the kinase domain of DAPK-1. Peptides bound to DAPK-1core kinase domain fragments had homology to the N-terminal domain of the microtubule-associated protein MAP1B. Immunobinding assays demonstrated that DAPK-1 can bind to the full-length human MAP1B, a smaller N-terminal miniprotein containing amino acids 1-126 and the 12-amino acid polypeptides acquired by peptide selection. Amino acid starvation of cells induced a stable immune complex between MAP1B and DAPK-1, identifying a signal that forms the endogenous complex in cells. DAPK-1 and MAP1B co-expression form a synthetic lethal interaction as they cooperate to induce growth inhibition in a clonogenic assay. In cells, two co-localizing populations of DAPK-1 and MAP1B were observed using confocal microscopy; one pool co-localized with MAP1B plus tubulin, and a second pool co-localized with MAP1B plus cortical F-actin. Reduction of MAP1B protein using short interfering RNA attenuated DAPK-1-stimulated autophagy. Transfected MAP1B can synergize with DAPK-1 to stimulate membrane blebbing, whereas reduction of MAP1B using short interfering RNA attenuates DAPK-1 membrane blebbing activity. The autophagy inhibitor 3-methyladenine inhibits the DAPK-1 plus MAP1B-mediated membrane blebbing. These data highlight the utility of peptide aptamers to identify novel binding interfaces and highlight a role for MAP1B in DAPK-1-dependent signaling in autophagy and membrane blebbing.
Highlights
Sitol 3-kinase, and calcium-calmodulin kinase family [1,2,3]
The calcium-calmodulin kinase family of protein kinases play a specialized role in coordinating certain cellular responses to distinct stresses such as p53 responses that include the DNA damage-activated kinase network of ATM-CHK2 (6 – 8), the metabolic kinase axis of LKB-AMPK [9], and oncogene activation mediated by ERK-DAPK-1 [10, 11]
In this study we focus on developing a linear interaction peptide consensus for the core kinase domain of DAPK-1 using peptide-aptamers, and we characterize one interaction that occurs with the microtubule-associated protein MAP1B
Summary
Sitol 3-kinase, and calcium-calmodulin kinase family [1,2,3]. These kinases are usually regulated post-translationally through modifications, including phosphorylation or ubiquitination to permit rapid responses to changes in environmental or diseased states [4]. Data are presented demonstrating a genetic and biochemical interaction between MAP1B and DAPK-1 that reduces cultured cell growth independently of apoptosis and stimulates membrane blebbing dependent on an active autophagic program.
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